Atmospheric icing takes place when water droplets in the atmosphere freeze on a contacted object. For example, in connection with aircrafts the ice may increase the risk of stalling of the airfoil. Thereby, the ice built-up should be detected as early and reliably as possible. For instance, an electromechanical probe with an oscillating (vibrating) sensing element may be provided on the nose of the aircraft, whereupon the ice accreted thereon causes changes in the oscillation frequency depending on the thickness of the ice layer. The oscillation frequency is monitored for estimating the amount of ice.
As another use scenario, the wind turbines of wind farms may be heavily affected by ice on the rotor blades. The blades may crack and the production efficiency may drastically decrease. The overall wear of the turbine may also increase due to mass and aerodynamic imbalances and resulting friction caused by the ice. Introduction of the aforesaid oscillating probe into the nacelle of a wind turbine has been suggested, so has been the use of various capacitance-, impedance-, and inductance-based detectors requiring the addition of specific sensors on the rotor blades. Further, different optical sensors monitoring the ice accumulated on a sensor surface based on e.g. changes on light reflection from the surface have been set forth.
To prevent or reduce icing, a number of anti-icing or de-icing procedures such as heating or microwave excitation procedures have been set forth to prevent, reduce or slow down ice accretion on predetermined surfaces. Heating may be implemented via blowing hot air or other gas, funneling heated wires, other elements or e.g. liquid, a liquid circulation system, to the target area(s). For anti-icing use the target areas may include ice-repellant coating such as silicon paint, for example.
Many known arrangements to prevent icing still suffer from reliability, efficiency and/or safety problems at least in certain type of operational conditions.
For instance, in the context of aviation and wind farms, the required heating capacity may be about 10 kW/m2 in magnitude. If the connection between the target surface to be heated and the applied heating element is inadequate and fails, both the surface and the element may be damaged due to overheating.
In some scenarios, extremely thin metallic conductors such as wires or e.g. metallized fibers have been laminated in epoxy and provided onto the target surface. However, these arrangements are extremely prone to mechanical breakage due to fatigue caused by various potential factors such as repeated bending or moisture between the laminate layers, which easily leads to heating malfunction such as reduced or completely ceased heating without forgetting, on the other hand, the risk of overheating. In addition, the contemporary solutions may be extremely tricky to dispose on the target surface, such as rotor blade, without sacrificing some design requirements as to the thickness, weight, airfoil, etc. thereof.